[molpro-user] Isotopologue VSCF with Potential from PESTRANS

[Guntram Rauhut]

Dear Dennis,

actually, what you are doing is the proper way of doing it and you 
cannot avoid the 3 transformations of the potential. Let me explain 
this: The SURF program calculates the potential in term of grid points. 
As you want to compute isotopic effects you need to span the potential 
in terms of the new mass-weighted normal coordinates. This can only be 
done once an analytical representation of the potential is available. 
Therefore you need to transform the grid representation to a polynomial 
one with the POLY program prior to the call of PESTRANS. For technical 
reasons PESTRANS always provides a grid representation. At this point 
(after the call of PESTRANS) you may decide what to do. You can use the 
grid-based VSCF and VCI programs directly, which means that you may 
avoid the POLY call after the PESTRANS program. However, as the 
polynomial based VSCF/VCI programs are usually much faster, it is 
advantageous to call POLY again (as you do) and run then the polynomial 
based VSCF/VCI programs.

Looking at your input I realized that the call of the VRC card is not 
consistent. Once you do not put it as an option to the SURF program, 
VRCs are not calculated. As a consequence, they cannot be used later on.

I hope, this helps,

     Guntram



On 07/10/17 17:25, Dinu, Dennis Florian wrote:
> Dear Molpro-Team,
>
> I need a hint on a rather simple problem. Currently I am trying to get 
> into MOLPROs capabilities of calculating anharmonic vibrational 
> spectrum (e.g. VSCF) of isotopologues with the PROGRAMS: SURF, POLY 
> and PESTRANS.
>
> The specific example is to obtain the spectrum of deuterated water 
> "HDO", by transforming the PES of a previous calculation of 
> non-deuterated water "H_2 O".
>
> I use the following input for the calculation:
>
> -----------------------------------------------------------------------
> ***,h2o vibrational test
> memory,64,m
> gprint,orbitals,basis
>
> geometry={
> O
> H1,O,B1
> H2,O,B1,H1,A1
> }
> B1=  0.95907103 ANG
> A1=  103.51462331 DEGREE
>
> orient,mass
> mass,iso
>
> basis=vtz
>
> hf
> mp2
> optg
>
> label1
> {hf
> start,atden
> }
> mp2
>
> {surf,start1D=label1
> disk,where='scr',extern='h2o_1D2D3D_mp2_di_vrc.pot'}
>
> poly,dipole=1,vrc=1
>
> {pestrans,vrc=1,plot=3
> intensity,dipole=1
> mass,2,2.01410178d0}
>
> poly,dipole=1,vrc=0
>
> vscf,type=poly,dipole=1,combi=2,ubound=10000
> vci,type=poly,vam=3,dipole=1,combi=2,ubound=10000
>
> put,irspec,irspec.dat
>
> -----------------------------------------------------------------------
>
> This yields the correct results, but as you can see, i need to 
> transform the initial PES three times! I think there should be a more 
> sensible way of doing this?
>
>
>
>
> _______________________________________________
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> Molpro-user at molpro.net
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-- 
********************************************************************************

  Apl. Prof. Dr. Guntram Rauhut
  Institut f. Theoretische Chemie
  Universitaet Stuttgart
  Pfaffenwaldring 55
  D-70569 Stuttgart
  Germany

  Tel. :   +49/(0)711/685-64405
  FAX :    +49/(0)711/685-64442
  E-Mail : rauhut at theochem.uni-stuttgart.de
  HTTP :   www.uni-stuttgart.de/theochem/rauhut/

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